Abstract
In this report we describe repurposing of recycled polyesters as a matrix for lignin-a biorefinery coproduct that is used as a solid fuel and needs to find higher value-to make sustainable high-performance thermoplastic materials. Brittle lignin oligomers, isolated from plant biomass, require a low-melting host polymer matrix to form a rigid and tough renewable material. We demonstrate controlled lignin dispersion and interfacial interactions in softened recycled polyethylene terephthalate (PET) using a simple solvent-free, melt-blending technique. To avoid lignin degradation and devolatilization during melt processing, it was thermally treated. Tall oil fatty acid was used to enable PET processability at low enough temperature to accommodate lignin without charring. Chemical analysis reveals reduction of aliphatic hydroxyl content from 2 mmol g-1 to 1.63 mmol g-1 and an increase of total phenolic hydroxyl moieties from 5.86 to 6.64 mmol g-1 and cleavage of β-O-4 ether linkages due to thermal treatment. Structural transformation of lignin macromolecules during heat treatment was further confirmed by an increase in molar mass and improved thermal stability. Interfacial interactions between lignin and PET were assessed from mechanical properties and thermal analyses. Thermal treatment not only helps to improve the stability of lignin but also slightly reduces the size of the dispersed lignin domains via favored interfacial interactions with the PET matrix. These methods improve mechanical properties of the material. Further, incorporation of lignin in the plasticized PET matrix increases the ductility in the blended products. The method we discuss here utilizes industrial wastes and co-products, and it does not require solvent or toxic chemicals during the reactive extrusion process that yields complete conversion to products.
Original language | English |
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Pages (from-to) | 31202-31211 |
Number of pages | 10 |
Journal | RSC Advances |
Volume | 9 |
Issue number | 54 |
DOIs | |
State | Published - 2019 |
Funding
This project is supported by the Sun Grant Initiative and by Agriculture and Food Research Initiative Competitive Grant no. 2014-38502-22598 from the USDA National Institute of Food and Agriculture and by the USDA National Institute of Food and Agriculture, Hatch project 1012359. N. A. N. acknowledges support from the U. S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, BioEnergy Technologies Office Program for the rheological analysis of the materials. A. K. N. acknowledges support from the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the US Department of Energy. † This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). ‡ Electronic supplementary information (ESI) available. See DOI: 10.1039/c9ra07052d